Read this if you own a Karcher..

This isn't Jimny related as such, but I thought this would be useful information for everyone out there who owns a Karcher. As everyone reading this owns a 4x4 I suspect that's most of you..

My Karcher K4 premium had developed a really strange intermittent electrical fault, where it would trip the RCD in the garage fuse board. The machine would trip the fuse sporadicly with no prior warning or loss in performance. After a second electrical trip in 48 hrs, I knew the machine was going to be coming apart. The pressure washer was just outside of warranty period (I know Sod's law).

(RCD's "residual current devices" do not protect against electrical overcurrent i.e drawing too much power, they protect against short circuits, imbalances between L + N, faults to earth etc. So in essence if your appliance is tripping one, you can be sure it has an electrical fault within.

So I pulled it apart and this is what I found......

Karcher K4 premium water cooled motor.



First test I ran was electrical continuity (Ohms) through the main lead, motor and through the switch/capacitor housing (white thing) using a multi meter. All was fine.. very low in fact the head scratching continued.



So that's it then, motor is coming apart! Cylinder head, Capacitor & switch housing removed Continuity tested again on the bench (all good). Notice the little electrical Piezo? the white electrical housing sits on top of that, along with the actual high pressure pump. That is the means of sending power to the electrical motor below. A series of tap washers and that little rubber gasket is all that's stoping the machine from arcing out! No sign of water + arcing here though - so the search continues.




So the main lower motor housing was then split apart:





Oh dear... As you can see from the above photographs, the water cooled void of the motor (see where my screwdriver is) seems to have been 'letting by'. The cheap o-rings aren't up to the job, they didn't seem like a nice snug fit. As you can see there seems to be arcing marks present on the main internal motor housing, right beside the 2kw coil.. we've found our tripping source!

So the reverse begins, I built the motor housing back up using RTV gasket sealant.



The cylinder head was then stripped inspected and re-greased with moly axle grease - as the existing factory grease seems to have been contaminated with water and gone all mushy. The machine works by a motor spinning an offset wobble plate, this compresses the three little valves in sequence which in turn provide compression to the water pump above, Quite simple, just assembled cheaply.

See continuation...

I also used RTV sealant on the Cylinder head O-ring.

The machine was then bled, and bench run with great success.



I ran the machine continually for about 20 minutes with a high pressure lance whilst drinking a cup of well earned tea. No more Tripping, the machine sounded quieter and also featured slightly increased pressure at the lance.

In summary, I think Karcher machines are over priced and cheaply made. There seems to be a couple of minor design flaws present here with this K4 premium, not what you expect for £300+. If you suffer a similar issue with your water cooled Karcher the above checks for water around the cylinder head and within the motor housing should be your go to! Check for chalky aluminium corrosion and arching marks (as photographed above)

If I was to have my time again, I'd buy a small portable petrol pressure washer. Water and electricity will never be friends Hope this helps a few others!

Bloody good work on finding the source of the problem. I tend to agree with you on your remark about Karcher being overpriced but cheaply made & put together - my dad has had three to date and they never lasted despite using them well within the scope of what it is made for.

Maybe I'll have a go at fixing his current one when it decides to break...

Reason2doubt wrote: Bloody good work on finding the source of the problem. I tend to agree with you on your remark about Karcher being overpriced but cheaply made & put together - my dad has had three to date and they never lasted despite using them well within the scope of what it is made for.

Maybe I'll have a go at fixing his current one when it decides to break...

Ditto, this is my second Karcher in 5 years. I had a cheap K2 air cooled variant before hand which gave up the ghost after about 18 months. (1 year warranty)

I've had numerous attachments break too - which cost a small fortune to replace...

This will probably be my last Karcher

Ditto again.
I purchased a Karcher to replace my "cheap make washer of 5 years" expecting it to be so much better. 1st one burnt out at 10 mount light use, it's replacement has already been apart numerous time to fix leaks and breakages. Cheap junk now unfortunately, last one I will purchase.

Me too, bought 2 and they both broke after 18 months. Never again. I only use 'em 2 or 3 times a year too, shocking.

My at least 30 year old first gen Karcher is still trouble free touch wood, but like all 'progress', the build quality/components make be lesser now

Excellent piece of investigative research and problem solving. Looks like Karcher have been too busy 'value-engineering' their product and it fails just outside of warranty! Wonder what the cost of the 'O-Rings' that failed was? Another example of the built-in obsolescence culture that is foisted upon us?

Thanks Bob!

I checked the website 'e-spares' to try and cost the replacement parts that I suspected faulty.

www.espares.co.uk/browse/mt15/pressure-w...r/domestic-k4-series

The parts seem quite expensive. For instance a complete new motor is circa £220 I'm sure if you shopped around you'd find all of the spares required, that's one bonus to the big brand name I suppose.

Just disappointing that Karcher design engineers have thrown all of that R&D into designing 'market leading' pressure washers, but then skimp on things like gaskets and seals that are almost guaranteed to fail in a short number of years. Not what you expect for £300+ of her majesties pound sterling.

Great work. Photos and commentary. Would have attempted repair of two previous Karchers if I’d had this. Thank you

RumbleAndSway wrote: Great work. Photos and commentary. Would have attempted repair of two previous Karchers if I’d had this. Thank you

Always like guys with an enquiring mind and a willingness to freely share 'useful' information. That's another of the advantages of forums and the interwebby. Good guy is Dagzook or as a red-top tabloid might put it "The Boy Done Good" = Thank you Sir!.